1. Field of the Invention
The present invention is directed to an electrical switch for use with an automatic transmission of an automobile, and more particularly to a rotary electrical switch which is in use to be interlocked with the automatic transmission for detecting the positions thereof and for controlling electric circuits associated with the positions of the automatic transmission.
2. Description of the Prior Art
Electrical control switches for an automatic transmission of an automobile have been known such as disclosed in Japanese Utility Model Publication (Kokoku) No. 1-19772 published on June 7, 1989 and in U.S. Pat. No. 3,602,656. The switch comprises a switch casing and an actuator which is interlocked with a control shaft of an automatic transmission to be rotatable together therewith. The switch casing is composed of a base plate and a cover plate which are coupled together to rotatably support the actuator therebetween. A plurality of fixed contacts are arranged on the interior of the base plate in correspondence to positions of the automatic transmission, i.e., "Parking", "Reverse", "Neutral", "Drive", "2nd", and "Low" positions. The actuator carries a movable contact which moves across the fixed contacts as the actuator rotates about a rotation axis for conduction between selective sets of the fixed contacts to energize or deenergize a corresponding one of electrical circuits or loads associated with the positions of the transmission. In prior art switches, however, the fixed contacts are disposed only on the side of the base plate, so that they should be arranged at positions spaced from the rotation axis of the actuator by a relatively greater distance in order to provide enough clearance between the adjacently disposed fixed contacts arranged circumferentially about the rotation axis. This arrangement will inevitably add an extra dimension to the base plate and therefore the switch housing itself, particularly with respect to the radial direction as measured from the rotation axis to the respective fixed contacts. Also with this arrangement of providing the fixed contacts only on the base plate, the base plate suffers from jamming of conductor members leading from the fixed contacts respectively to individual terminal pins, which also makes it difficult to attain a compact design of the switch of this kind. Thus, the prior electrical rotary switch is not satisfactory in providing a more compact design.